The present invention relates to biarylbisphosphines and intermediates thereof. Furthermore, the scope of the invention encompasses catalysts which can be prepared from the bisarylphosphines and their use in asymmetric syntheses.
Enantiomerically enriched biarylbisphosphines, particularly those derived from substituted binaphthyls and biphenyls, when used as ligands in transition metal catalyst complexes often lead to good to very good enantioselectivity (cf., for example, Helv. Chim. Acta 1988, 71, 897-929; Acc. Chem. Res. 1990, 23, 345-350; Synlett 1994, 501-503; Angew. Chem. 2001, 113, 40-75).
Steric and electronic factors which are determined by the type and arrangement of substituents on th biaryl system or within the phosphine groups influence both the enantioselectivity and the activity of the catalysts prepared from such ligands.
In individual cases, Rh and Ru catalysts of this type are used industrially for enantioselective C═C double bond isomerizations and for enantioselective hydrogenations. The number of such industrial processes has hitherto been restricted because the number of available ligands which can successfully be used broadly for a large number of substrates is small. Rather, the comprehensive studies in this field show that, owing to the substrate specificity which is an in-principle property of the catalyst which is often “tailored” for a very specific substrate, even slight changes within the same substrate group does not allow the required enantiomeric purity to be achieved for a very similar product.
EP-A 643 065 and EP-A 749 973 disclose representatives of biphenylbisphosphines which are substituted in the 5,5′ and 6,6′ positions and which enable the catalysts obtainable from these ligands to be matched to particular substrates by varying the phosphane substituents, so that optimized enantioselectivities are achieved.
However, there continues to be a need to provide a group of ligands and catalysts which can be prepared therefrom which make possible both a generally high level of enantioselectivity and activity and allow matching to a particular substrate in a simple fashion by varying the substituents on the ligand system.